This invention relates generally to the field of orthopedic surgery, and in particular to total knee replacements. More specifically, the invention relates to the treatment of an infected total knee replacement.
In the United States, about 600,000 total knee arthroplasty procedures (also known as total knee replacements) are performed each year. A typical total knee replacement procedure involves resurfacing of the tibial plateaus and the femoral condoyle. Holes are then drilled into the femur and the tibia. A metallic femoral component is then inserted into the femur and a metallic tibial component is inserted into the tibia. Bone cement usually holds the two components into place. These two components work together to replace the diseased knee joint and to simulate the function of a normal knee joint. One example of a total knee replacement surgery is described in U.S. Pat. No. 6,342,075, the complete disclosure of which is herein incorporated by reference.
About two to three percent of total knee replacements become deeply infected. When these components are simply replaced by new components, the rate of cure of the infection is low compared to a two-stage surgical treatment where the components are removed and the infection treated before new components are reimplanted. In such cases, some have proposed removing the femoral and tibial components and replacing them with a puck-shaped spacer or void shaped spacer made of bone cement that is impregnated with an antibiotic or a fixed mass of antibiotic impregnated cement that fills the dead space left by the removal of the infected prosthetic components. This is placed between the femur and the tibia for six to twelve weeks. The antibiotic in the puck or cement mass leaches out over time to treat the infection. When the infection is contained, the puck is removed and the femoral and tibial components are once again inserted. Such a process is described in U.S. Pat. No. 5,980,573, the complete disclosure of which is herein incorporated by reference.
One problem with the use of such a spacer is that there is no knee joint while the infection is being treated. As such, the leg cannot move or bend. Often the spacer is loose and painful and the knee will scar down and will stiffen up, resulting in painful rehabilitation, loss of final normal range of motion and function, among other ailments. This also makes the final replacement surgery itself technically more difficult because of the scarring and loss of motion and knee joint space at the time of reimplantation of new permanent components.